The correlation of damping capacity with grain-boundary precipitates in Fe–Cr-based damping alloys annealed at high temperature

We report the damping capacity measurements and grain-boundary (GB) precipitates observations on a set of four Fe–Cr-based ferromagnetic damping alloys annealed at 1473K. The alloys were prepared by vacuum induction melt furnace of which each cast ingot weighed 15kg. The technique of inverted torsion pendulum was employed to measure the damping capacity, and a field emission scanning electron microscope (FESEM) with a X-ray energy dispersive spectrometer (EDS) attachment was used to observe the grain-boundary precipitates. The results indicate the damping capacity of the alloys is definitely correlated with the amount of the grain-boundary precipitates as well as with the chromium concentration in the precipitates. Among the alloys investigated, Fe–Cr–2Al–Si exhibits the highest damping capacity but the least amount of grain-boundary precipitates with the lowest chromium concentration, and vice versa to that Fe–Cr–Al–Si(L) does. Though chromium concentration in the grain-boundary precipitates are very close, the amount of grain-boundary precipitates in Fe–Cr–Al is obviously less than that in Fe–Cr–Si, and the damping capacity of the former is apparently higher than that of the latter. Further discussion pointed out such correlation stems from the effects of alloying on the diffusion behavior of solute atoms as well as on the chemical potential of Cr in the matrix, with which correlates the magnetic properties especially the energy density of domain walls (DWs) which has a significant impact on the damping capacity of Fe–Cr-based damping alloys annealed at high temperature.